Force amplifying device for winding a rope under tension

ABSTRACT

A force amplifying device for stretching sail and riggings of a sailing device. The device includes a rope drive for winding up a rope under tension arranged in an elongated housing with the axis of the rope drum directed essentially perpendicular to a longitudinal extension direction of the housing. An elongated crank arm is arranged outside the housing in a force transferring connection to the rope drum for turning the rope drum and winding up a rope under tension on the rope drum. At least one locking arrangement is provided for locking the crank arm in a direction which substantially coincides with the longitudinal extension direction of the elongated housing.

BACKGROUND OF THE INVENTION

The development within the windsurfing area is towards higher and morenarrow sails, especially for funboards, which require higher masts,usually with an extension of the mast from previously 4.50 m to about4.90 m, which can be achieved with a mast extender arranged at the lowerend of the mast. Furthermore, new stiffer materials are used for thesails, such as "Kevlar" and "Mylar". Such new sails are less extensibleand require the use of larger forces for stretching the sail along themast and along the boom (fore or mast leech and boom leech).

SUMMARY OF THE INVENTION

According to this invention these problems are solved by arranging in orat the lower end of the mast or a mast extender intended to be arrangedat the lower end of the mast a force amplifying device for stretchingand locking the fore end of the sail, i.e. the fore leech. With saidforce amplifier a fairly small force applied by hand can be amplified,for example with at least 50%, preferably at least 200% and especiallyat least 300% or 500%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross section through a mast extender according to afirst embodiment of the invention;

FIG. 2 is a partial cross section view of a preferred embodiment of theinvention arranged in a mast device;

FIG. 3 is a side view of the embodiment according to FIG. 2;

FIG. 4 is a view in the axial direction of the mast of the embodimentaccording to FIG. 2;

FIG. 5 is a partial cross section view of a further preferred embodimentof the invention;

FIG. 6 is a side view of the device according to FIG. 5 viewed in adirection perpendicular thereto;

FIG. 7 is a view in a direction perpendicular to the view directions ofFIGS. 5 and 6 of the device according to FIG. 5;

FIG. 8 is a side view of the device according to FIG. 5 arranged on asail-boom;

FIG. 9 is a side view of the device according to FIG. 5 arranged on asail-boom; and

FIG. 10 is a side view of the device according to FIG. 2 arranged fortensioning a sail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferably the force amplifier is arranged within the lower part of themast or the mast extender. One such device is shown on FIG. 1 which ispartly a section through a part 1 of a mast or mast extender andcomprises a two-fold purchase with a fixed block 2 with 4 wheels 3arranged in parallel on the same axis 4 which extends through holes inthe mast (or extender) 1 and cooperates with a similar second block 5with 4 wheels 6 arranged on the same axis 7 which extends through twolongitudinal openings 8 in the mast. The two blocks 2 and 5 areconnected with a rope 9 in the usual way for such a per se known device,and one end 10 of said rope extends through an opening 11 in the mast atwhich there is arranged a pulley wheel or a similar device which permitspassing the rope out from the inside of the mast with a low friction.The movable block 5 is provided with a fastening means 13 for one end ofa second rope 14, the other end 15 of which extends through an openingin the mast, preferably via a first pulley wheel 16 and a second pulleywheel 17 arranged at an opening 18 in the mast. The outer end 15 of theropes 17 is secured to the tack 19 of a sail as is shown sketchily onthe figures. A force applied in the direction of arrow 20 will thuscause an amplified force acting in the direction of the arrow 21 on thesail.

FIGS. 2-4 show a preferred embodiment of the invention according towhich a mast extender 1 or a mast end is provided with a rope drum 2with a cylindrical part 4 on which a rope 5 which is secured to the drumcan be winded up by turning the rope drum 2. The rope drum may beprovided with end flanges 3, 3' but these are not absolutely necessaryand the drum may consist of a straight, preferably cylindrical shaft.The rope drum can be turned with the aid of a crank 6 or a fulcrum whichis arranged on the outside of the mast extender or mast and is connectedto the rope drum. According to the figure this connection is provided bya shaft 7 on which the rope drum is arranged, said shaft 7 being mountedin bearings in opening 8 in the mast extender or mast. Said openings mayoptionally be provided with bushings. The ends of the rope drum, such asthe flanges 3, 3', may function as stopping means for the axial movementof the rope drum within the mast or mast extender. The end of the crankarm 6 is provided with a locking means, preferably consisting of a bolt9, which is held slidably in an opening at the end of the crank arm 6and can be displaced towards the mast extender or mast and be lockedinto a locking means thereon, which on the figures is shown as openings10, 10' in the mast or extender wall. The device is provided with atleast one such locking means 10, 10' and preferably with two lockingmeans arranged one on each side of the rope drum in the longitudinalextension of the mast or extender, said locking means preferably beingarranged essentially on a straight line in said longitudinal directionwith the rope drum in the middle therebetween. The outer end of thedisplacable locking means 9 may be provided with a gripping means, suchas a knob 11, a ring or a similar means in order to facilitate thegripping and turning of the crank 6. The rope 5 extends through anopening 12 in the mast or extender wall and is preferably passed over apulley wheel 13 which may be arranged in a bracket 14 secured to themast or extender wall. The outlet opening 12 is on FIGS. 2 and 3 shownarranged closer to the lower end than the rope drum 12 but may also bearranged at the same level or on a higher level, i.e. further away fromthe lower end of the mast or extender than the rope drum 12, in whichcase the pulley wheel 13 may be disposed of or substituted with asimpler bushing means arranged in the outlet opening for the rope, andthe last-mentioned embodiment is indicated with a rope 5' shown withbroken lines on FIG. 3.

The rope 5 is connected in a force-transferring way to the fore leech 15of a sail, preferably with a pulley wheel 16 or a similar device, inwhich case the other end of the rope 5 is fastened at 17 to the lowerend of the mast or extender, e.g. to the mast step 18 or preferably to afastening means arranged at the mast or extender or the mast step and towhich the rope 5 can easily be detachably secured, such as a clam cleat(not shown). By passing the rope over a pulley wheel 16 or a similardevice the tension exerted on the sail 15 by the rope 5 will beincreased to about two-fold of the tension exerted on the rope by therope drum 2.

Before stretching the lower end of the sail towards the end of the mastor extender the rope is preferably winded off from the drum 2 to thefull extent and the sail is then stretched with the aid of the free endof the rope 5, which is then locked in a locking device such as a clamcleat. The stretching of the sail is then continued by winding up therope on the drum 2 until a suitable tension is obtained and the drum 2is then locked by locking the crank arm 6 with locking means 9, 10. If asuitable tension cannot be obtained with the crank arm 6 in suitableposition for locking, the end of the rope 5 is locked in the lockingmeans in a new position which permits turning the crank arm 6 to aposition in which the locking means 9, 10 can cooperate, with suitabletension exerted on the sail. It is usually preferable that the diameterof the rope drum is as small as possible so that the increment of ropewinded up on the drum 2 is as small as possible for each 180° turn ofthe crank arm 6 and drum 2. Thus the diameter of the rope drum 2 may beselected to at most 30 mm, preferably at most 20 mm or at most 15 mm orat most 10 mm. The extension of the crank arm 6 should be sufficient forpermitting the user to conveniently exert a suitable tension on the sailbut should preferably be selected as small as possible in order toreduce the distance from the end of the mast or extender to theuppermost locking means 10 since usually the sail cannot be stretchedbelow said uppermost locking means. A suitable extension of the crankarm 6 may be at least 50 mm, usually at least 75 mm but preferably atmost 200 mm or at most 150 mm or at most 125 mm. The rope 5 may suitablybe connected to the drum 2 by passing it through a hole 19 in the ropedrum and being locked e.g. with a knot or a suitable locking means whichcannot pass through said hole 19.

The means connecting the rope 5 with the sail 15 may also comprise anelastically resilient means, such as a rubber spring or a screw springwhich optionally may be pre-stressed so that said spring means will beextended only when the tension in the rope 5 exceeds a desired lowerlimit.

The rope drum 2 may also be provided with other types of locking means,such as a ratchet means with release means, with which the drum may belocked in a suitable number of positions within each full turn of thedrum 2. The crank arm 6 is then suitably releasably connected to thedrum 2, e.g. with a free-wheel means or optionally completely removablefrom the drum 2 or axis 7. Furthermore, the locking means 10' andespecially the upper locking means 10 may be supplemented with a lockingmeans connected e.g. to the sail for holding the crank arm 6 in a properposition, preferably along the mast or in a position which preferablydoes not deviate more than 45° and especially not more than 30° or 20°from the length axis of the mast. Such a means is on FIG. 3 exemplifiedwith a simple rope loop 20 indicated with broken lines with the positionof the crank shaft 6 in relation to the sail likewise shown in brokenlines. (The position of the crank arm 6 in this case is, of course, theposition shown in full lines on FIG. 3). In this way the crank arm 6 canbe locked in the upper position also when the sail is stretched downbelow the upper end of the crank arm and below the locking means 10.

The force amplifying device according to the invention comprising a ropedrum enclosed in an elongated housing with a crank arm extending outsidesaid housing and with locking means for locking the crank arm in atleast one position and preferably at least two positions with the crankarm extending essentially in the longitudinal direction of the elongatedhousing is also ideally suited for other sailing devices thanwindsurfers and also for other purposes. Such a separate forceamplifying device which can be arranged on a suitable location e.g. withbolts or screws is shown on FIGS. 5-7. An elongated housing 1 ofrectangular cross section comprises a rope drum 2 connected to a shaft 7resting in bearings 8 in the wall of the housing consisting of openingsin said housing which may be provided with bushings. The devicecomprises essentially the same elements as the device disclosed on FIGS.2-4, such as a crank arm 6 with locking means 9 cooperating with lockingmeans 10 and 10' consisting of openings in the wall of the housing intowhich the locking means 9, which consists of a bolt, can be inserted.The outer end of the locking means 9 is also provided with a knob or aring or a similar means which facilitates gripping and handling. Therope 5 can be passed out from the housing through the open ends of thehousing or through one or more openings 22 arranged in the upper wall 23of the housing, as indicated with the rope 5'. The device can be securedto a suitable support with screws or bolts through openings 24.

FIG. 8 shows said device secured to a boom 25 of a sailing boat with thedevice used for stretching a sail 26. FIG. 9 shows the same devicearranged for hauling down the boom 25 along a mast 26.

FIG. 10 shows the device according to FIGS. 2-4 arranged in a mastextender 1, to which is secured a mast 27. The same reference numbersare used as on said figures for various parts. The end of the rope 5 isreleasably secured to a clam cleat 28. Furthermore, the end of the mastextender is connected to a rubber joint 29 provided with a screw 30intended to be joint to a mast foot (mast step) intended to be securedto a windsurfing board.

The ratio of the distance from the end of the crank arm 6 or knob 11 tothe centre of the shaft 7 relative to the radius of the rope drum 2 andthus the theoretical force amplification is preferably at least 2:1,especially at least 4:1 or at least 6:1 or even at least 8:1 or at least10:1.

I claim:
 1. A force amplifying device which comprises a rope drum forwinding up a rope under tension arranged in an elongated housing with anaxis of said rope drum directed essentially perpendicular to alongitudinal extension direction of said elongated housing, an elongatedcrank arm arranged outside said housing and extending a maximum of 200mm from said axis of said rope drum and being connected to said ropedrum for turning said rope drum and winding up a rope under tension onsaid rope drum, a ratio of a distance from a handle at an end of thecrank arm to said axis relative to a radius of said rope drum being atleast 4:1, and locking means for locking the crank arm in at least oneof two directions which substantially coincide with the longitudinalextension direction of the elongated housing, said locking meanscomprising a bolt which is arranged slidably in an opening at the end ofthe crank arm in a transverse direction to said crank arm, said boltbeing movable from an outer position in which the bolt acts as saidhandle for facilitating the gripping and turning of the crank arm, andtowards said housing to an inner position in which the bolt fits into alocking opening in the housing for locking the crank arm in said atleast one of said two directions which substantially coincide with thelongitudinal direction of the elongated housing.
 2. A force amplifyingdevice according to claim 1 arranged for stretching sail or riggings ofa sailing device.
 3. A force amplifying device according to claim 2which forms a part of a mast device comprising a mast extender for awindsurfing device.
 4. A force amplifying device according to claim 2which forms a part of the lower end of a mast for a windsurfing device.5. A force amplifying device according to claim 1 in which said housingcomprises a lower end part of a tubular mast device for connection to awindsurfing device, the longitudinal direction of said housing being thelongitudinal axis of said mast device, said rope drum being arrangedwithin said housing on a shaft supported in bearing means includingopenings in a wall of said tubular mast device, and at least one saidopening in the wall of the tubular mast device adapted for passing therope slidably out through said opening, said opening being arranged in aposition from which the rope, with one end connected to the rope drum,can be connected to a lower foremost end of a sail for tensioning saidsail towards said lower end of said mast device.
 6. A force amplifyingdevice according to claim 1 in which the ratio of distance from thehandle at the end of the crank arm to the radius of the rope drum is atleast 6:1.
 7. A force amplifying device according to claim 6 in whichthe said ratio is at least 8:1.
 8. The use of a device according toclaim 1 for stretching sails and riggings on a sailing device.
 9. Aforce amplifying device according to claim 1 including two lockingopenings in the housing for locking the crank arm in said two directionswhich substantially coincide with the longitudinal direction of theelongated housing, with said openings being on opposite sides of theaxis of said rope drum.